1. Field of the Invention
The present invention relates to thermoelectric modules and processes for producing the same. More particularly, the invention relates to a thermoelectric module using a small amount of material per unit output thereof, and a process for producing thermoelectric modules of the kind as described above in high yield and at low processing cost.
2. Description of the Prior Art
Conventional thermoelectric modules are produced by a process comprising cutting a melt-grown ingot thermoelectric material into bulk thermoelectric elements and bonding electrodes to the thermoelectric elements through soldering or the like technique. According to an alternative process, a chalcogenide alloy powder as thermoelectric elements is vacuum-sealed or sealed with inert gas in an ampule sintered to produce thermoelectric elements. Thermoelectric elements which are formed in these processes have a high figure of merit to provide an advantage of giving good thermoelectric conversion characteristics to thermoelectric modules.
However, the conventional production of thermoelectric modules in which use is made of an ingot thermoelectric material involves the following serious problems:
(1) since the yield of thermoelectric elements notably lowers when the thickness thereof is reduced to 1.5 mm or less, miniaturization of thermoelectric elements is difficult, with the result that the amount of a thermoelectric material used is inevitable large per unit output of a thermoelectric module and the material cost is high;
(2) because of cracking of a thermoelectric material in the cutting step and of high liability to poor electric conduction or short circuit across electrodes which is caused by failure in bonding of electrodes to thermoelectric elements through soldering or the like technique, the yield is notably lowered through the process of production of thermoelectric modules with high liability to formation of defective modules; and
(3) since thermoelectric elements not only are produced one by one but also are brittle, the automation of the production process is difficult and hence the processing cost is high.
The process in which use is made of sintering of a chalcogenide alloy powder has a problem of low productivity because pressure molding is necessary and moldings must be sintered in a state of being sealed in a container such as an ampule. And by this process, thermoelectric elements are produced one by on in the same manner as the former process, so that the automation of the production process and the reduction of the processing cost are difficult.